Energy and momentum resolved band structure of K<inf>2</inf>O: Electron momentum spectroscopy and linear combination of atomic orbitals calculation

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Journal Article
Journal of Physics Condensed Matter, 2003, 15 (41), pp. 6955 - 6968
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This paper details an experimental and theoretical investigation into the electronic structure of the highly ionic, alkali oxide, potassium oxide (K 2O). The experiments were carried out using the relatively new technique of electron momentum spectroscopy. This is an electron impact technique that is capable of measuring the electron intensity distribution as a function of energy and momentum. Calculations were performed within the linear combination of atomic orbitals approximation using both Hartree-Fock and density functional theory formalisms. We have been able to map the band dispersions and intensities in the oxygen valence bands and potassium 3p and 3s bands for the first time. Overlap of the O 2s and K 3p binding energy peaks makes it difficult to extract the band gaps involving either of these bands. The O 2p and K 3s peaks are resolved, however, and we observe a gap of 30.4 ± 0.2 eV. This value is reproduced by the PBEO calculation. Intensities within the s bands are reproduced well by all our calculations, whereas the observed p bands show anomalous intensity at the T-point, which is not present in any of the calculations.
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